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(Help) Fixing exhaust stud

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Hello everyone, 

So one of the lower row exhaust studs started leaking alot of radiator fluid. I know the top row goes into where the valves are and the threads are visible when the valve cover is taken off. I read somewhere on the faq that the bottom row doesn't thread into any opening, so is something wrong with the head or does this particular stud hole connect with some cooling/water passage? Once I removed it water just spilled out.


I've never taken the head off or done anything to it, it's the original head and is stock.


The thread was pretty much ruined by the PO and I'ma need to heli-coil or time-sert because the stud only grabs on by a few threads and slips. So is this thread repair possible with engine still in car or do I need a lift engine out?


Thanks in advance!


(The stud that is missing is the one that leaks)




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Ouch.. this is an original unmodified car with all it's original bits:(


Sooo if I have to replace head, I have a full 82 320i M10, correct me if I am wrong but these cars came with a 121 head. Can the 121 head just go on without doing different pistons or changing anything in the block? 

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I would try a helicoil with the head on the car, you'll probably need a right angle drill or a very compact drill. Just have to be careful about drilling and threading the whole straight.


E21s never got 121 heads only e21 2.0l and 1.8l.


Another option is to get a motor or head and fuel injection out of a 1984-85 318i. These have a much better injection system.


I would also suggest cleaning the engine bay up especially the valve cover.

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Just to clarify the first two pictures are from the 2002,The 320i is a parts car, I took the tranny 5 speed, the diff, 320is seats, larger drum breaks from that car and put into 72 2002 that I am currently working on.




I think I'm going to take off the head and inspect in these coming days. Hopefully it's something that can be repaired. That way it's a lot easier to repair the thread.

(This is the 2002 with the leaking stud hole)


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6 minutes ago, AGAIN_03 said:

My question was if I could possibly take the 320i head and put into my 2002 (if my 2002 head is damaged beyond repair), but correct me if I'm wrong, it seems that I can't due to the injection system being part of the head.

You can plug the injector holes and use the e21 head if you have flat top 8.0 compression pistons. If you have other higher compression pistons I don't think it will work.


You could try putting some loctite on a new stud and see if that stops the leak.

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14 hours ago, AGAIN_03 said:

My question was if I could possibly take the 320i head and put into my 2002 (if my 2002 head is damaged beyond repair),

If you currently have a 121 head, those pistons aren't compatible with either an E12 or E21 head (the latter should be what's on that 320 motor) so you'll either have to repair your existing head or find another 121 head--unless you want to mess with swapping out pistons.  


I had a situation with my '69 (121 head) where one of the water passages--directly over the exhaust port--eroded through into the combustion chamber, allowing coolant to leak into #1 cylinder.  I pulled the head, and a local machine shop welded up the passage (and two others that were about to go), planed the surface flat again and I reinstalled the head.  That was nearly 30 years ago, and all has been well ever since.   


Hopefully yours is reparable..I just can't figure out how coolant is dribbling out an exhaust stud hole...the don't (or at least aren't supposed to) connect.



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The 72 2002 is all stock E12 head with matching block. Not sure what pistons are in there. (We'll find out soon)


@Son of Martyis right, I plan on taking off the head and sending it out to be looked and repaired professionally.


The water coming out of the stud hole is definitely strange, my only guess is that the PO screwed an exhaust stud way way to deep and made an opening. Luckily I haven't had any issues while running, oil hasn't ever mixed and I  never experienced coolant in cylinders.


I tried loctite on exhaust stud and unfortunately there just isn't enough thread left for it to grab onto.


Thank you for your input @Mike Self, it's very reassuring..haha. Hopefully I don't find myself posting "WTB E12 head" any time soon. I want to keep everything as original as possible and only do improvements that will improve driveability.






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